This invention relates to packages for hall-cells and more particularly to stress-free packages for hall-cells of the semiconductor type.
In addition to the protection from physical damage and from moisture and contaminants that is afforded a standard semiconductor device by a conventional package, the package of a semiconductor type hall-cell should meet other special criteria as well. The sensitivity of such hall-cells is subject to change with any physical force that may tend to distort or stress the semiconductor chip. Furthermore it is often desirable to locate the hall-cell as closely as possible to the source of magnetic field that it is intended to sense. Thus the package should additionally exert no stresses on the semiconductor hall-cell either by transmitting such forces or by differential expansion or contraction resulting from temperature changes therein, and the protective housing enclosing the chip should be thin.
A stress-free package for such a hall-cell would eliminate a major source in conventional packages of changes in hall-cell sensitivity with temperature and permit application of known techniques for temperature compensation within the chip (e.g. the integrated circuit with a hall-cell as described in U.S. Pat. No. 3,816,766 issued June 11, 1974) to produce a packaged hall-cell with a near zero temperature coefficient of sensitivity.
Conventional packages typically include a die-bonded connection between the chip and a metal or metallized supporting substrate, and differential coefficients of expansion with temperature of the semiconductor and the substrate are unavoidable. Conventional resin encapsulated packages are usually chosen to house hall-cells since they may provide a thin covering, enabling close placement of the hall-cell to a source of a magnetic field. However, hard resin coatings in contact with the encapsulated hall-cell tend to produce large physically distorting forces on the hall-cell.
It is therefore an object of this invention to provide a stress-free package suitable for housing a hall-cell.
It is another object of this invention to provide a hall-cell package having a uniformly thin protective covering over the hall-cell.
It is yet another object of this invention to provide a method for manufacturing a thin walled stress-free hall-cell package, wherein good control is maintained in the physical registration of the package elements during assembly.